Another way to get off vocals is to go on nicovideo add ニコカラ (nicokara) after the end of the song title. :3

Colorful Wall and Canvas White should have an off vocal since there are people who sing to the off vocal. That producer would post the off vocal on his piapro. http://piapro.jp/content_list/?pid=g9fried&view=audioHe did with all his other songs-- but not for that. "OTL